Several conditions may be confused with lupus (systemic lupus erythematosus, or SLE). They share some but not all of the symptoms of lupus. For example, rheumatoid arthritis begins with joint pain and swelling, and fibromyalgia begins with fatigue and joint pain. But as the condition continues, people with lupus develop skin rashes or symptoms in other organs, such as the heart, lungs, or kidneys, and will test positive for antibodies produced by the immune system that help to identify lupus.

Conditions that may have symptoms similar to lupus include:

• Arthritis (joint pain and restriction of movement), such as rheumatoid arthritis.
• Fibromyalgia, a disease of the muscles and joints that causes pain and stiffness.
• Rheumatic fever, a complication of an infection in the upper respiratory tract.
• Glomerulonephritis, inflammation of the kidneys.
• Scleroderma, a disease of the body's connective tissue.
• Sjögren's syndrome, a condition that causes dry mouth and dry eyes, and is often associated with rheumatoid arthritis.
• Chronic fatigue syndrome, a condition of severe, long-term fatigue.
• Vasculitis, inflammation of the blood vessels.